[tarantool-patches] [PATCH][vshard] Preserve route_map on router.cfg

[AKhatskevich <avkhatskevich@tarantool.org>]

Routes in `M.route_map` should be preserved to avoid redundant
discovery.

Closes #117
---
Branch: https://github.com/tarantool/vshard/tree/kh/gh-117-save-route-map
Issue: https://github.com/tarantool/vshard/issues/117

 test/router/router.result   | 42 ++++++++++++++++++++++++++++++++++++++++++
 test/router/router.test.lua | 24 ++++++++++++++++++++++++
 vshard/router/init.lua      |  7 +++++--
 3 files changed, 71 insertions(+), 2 deletions(-)

diff --git a/test/router/router.result b/test/router/router.result
index 2ee1bff..5643f3e 100644
--- a/test/router/router.result
+++ b/test/router/router.result
@@ -1057,6 +1057,48 @@ error_messages
 - - Use replica:is_connected(...) instead of replica.is_connected(...)
   - Use replica:safe_uri(...) instead of replica.safe_uri(...)
 ...
+--
+-- gh-117: Preserve route_map on router.cfg.
+--
+bucket_to_old_rs = {}
+---
+...
+bucket_cnt = 0
+---
+...
+test_run:cmd("setopt delimiter ';'")
+---
+- true
+...
+for bucket, rs in pairs(vshard.router.internal.route_map) do
+    bucket_to_old_rs[bucket] = rs
+    bucket_cnt = bucket_cnt + 1
+end;
+---
+...
+bucket_cnt;
+---
+- 3000
+...
+vshard.router.cfg(cfg);
+---
+...
+for bucket, old_rs in pairs(bucket_to_old_rs) do
+    local old_uuid = old_rs.uuid
+    local rs = vshard.router.internal.route_map[bucket]
+    if not rs or not old_uuid == rs.uuid then
+        error("Bucket lost during reconfigure.")
+    end
+    if rs == old_rs then
+        error("route_map was not updataed.")
+    end
+end;
+---
+...
+test_run:cmd("setopt delimiter ''");
+---
+- true
+...
 _ = test_run:cmd("switch default")
 ---
 ...
diff --git a/test/router/router.test.lua b/test/router/router.test.lua
index fae8e24..106f3d8 100644
--- a/test/router/router.test.lua
+++ b/test/router/router.test.lua
@@ -389,6 +389,30 @@ end;
 test_run:cmd("setopt delimiter ''");
 error_messages
 
+--
+-- gh-117: Preserve route_map on router.cfg.
+--
+bucket_to_old_rs = {}
+bucket_cnt = 0
+test_run:cmd("setopt delimiter ';'")
+for bucket, rs in pairs(vshard.router.internal.route_map) do
+    bucket_to_old_rs[bucket] = rs
+    bucket_cnt = bucket_cnt + 1
+end;
+bucket_cnt;
+vshard.router.cfg(cfg);
+for bucket, old_rs in pairs(bucket_to_old_rs) do
+    local old_uuid = old_rs.uuid
+    local rs = vshard.router.internal.route_map[bucket]
+    if not rs or not old_uuid == rs.uuid then
+        error("Bucket lost during reconfigure.")
+    end
+    if rs == old_rs then
+        error("route_map was not updataed.")
+    end
+end;
+test_run:cmd("setopt delimiter ''");
+
 _ = test_run:cmd("switch default")
 test_run:drop_cluster(REPLICASET_2)
 
diff --git a/vshard/router/init.lua b/vshard/router/init.lua
index 61c83d4..5674e04 100644
--- a/vshard/router/init.lua
+++ b/vshard/router/init.lua
@@ -480,8 +480,6 @@ local function router_cfg(cfg)
     log.info("Box has been configured")
     M.total_bucket_count = total_bucket_count
     M.collect_lua_garbage = collect_lua_garbage
-    -- TODO: update existing route map in-place
-    M.route_map = {}
     M.replicasets = new_replicasets
     -- Move connections from an old configuration to a new one.
     -- It must be done with no yields to prevent usage both of not
@@ -494,6 +492,11 @@ local function router_cfg(cfg)
     for _, replicaset in pairs(new_replicasets) do
         replicaset:connect_all()
     end
+    -- Update existing route map in-place.
+    for bucket, rs in pairs(M.route_map) do
+        M.route_map[bucket] = M.replicasets[rs.uuid]
+    end
+
     lreplicaset.wait_masters_connect(new_replicasets)
     if M.failover_fiber == nil then
         log.info('Start failover fiber')
-- 
2.14.1